1. Field of the Invention
The present invention relates to a fastening device with tape and a method of manufacturing the same. More particularly, it relates to a fastening device with tape in which an fastening device comprising either of a male member or a female member or both of the male and female members is integrally adhered on the same tape, and a method of manufacturing the same.
2. Description of the Related Art
It has been known for a long time to form at least one attachment hole in a single tape, and integrally mold an eyelet or a similar article made of synthetic resin with a desired shape onto front and back faces of the tape such that the eyelet or the article holds a peripheral edge of the attachment hole. As disclosed in U.S. Pat. No. 2,821,764, for example, an attachment hole is formed in a sheet material, and an eyelet made of synthetic resin with a desired shape is integrally molded on front and back faces of the sheet material so as to hold a peripheral edge of the attachment hole. The eyelet is molded as such by clamping the sheet material extending in an annular cavity for molding the eyelet, at a plurality positions at the peripheral edge portion of the attachment hole as a center, by using a plurality of pairs of pin members projecting in the cavity so as to face each other, and by introducing molten resin into the cavity.
In general, if the pin members do not exist in the above-described molding, the peripheral edge of the attachment hole of the sheet material extending in the cavity largely corrugates in a peripheral direction due to an introducing pressure of the molten resin. At worst, a portion of the peripheral edge may be deflected so as to abut on an inner face of the cavity, so that the sheet material may be exposed at a portion of a surface of the eyelet as a molded product. The invention disclosed in the above U.S. patent has been accomplished by taking notice of that a proper degree of corrugation of the peripheral edge of the attachment hole in the sheet material increases a strength of securing of the eyelet to the sheet material. In order to obtain the proper degree of corrugating state, the peripheral edge portion of the attachment hole of the sheet material is clamped by the pin members in the cavity, thereby controlling a degree of the corrugation.
In the above U.S. patent, an inlet for introducing the molten resin into the cavity is formed so as to face the peripheral edge of the attachment hole so that the molten resin introduced into the cavity by injection can smoothly flow to the front and back faces of the attachment hole of the sheet material. In other words, the molten resin introduced from a center of the annular cavity is guided toward an outer diameter in a plane including the attachment hole. The molten resin supplied from the inlet is forwarded respectively to the front and back faces of the sheet material at the peripheral edge of the attachment hole. With this structure, because the sheet material is incorporated with the eyelet at the peripheral edge of the attachment hole in a proper degree of corrugating state, the securing strength increases.
According to the above invention, however, a thin disk-shaped plate made of synthetic resin is integrally molded at a central opening portion of the molded eyelet, so that a peripheral face of the opening portion of the molded eyelet must be trimmed after removing the thin plate after molding as described in the specification.
There is a similar invention that follows the above technical idea of preventing excessive corrugation, which is as disclosed in European Patent No. 0228293. In the European patent, a fastener member of a snap fastener, not limited to a male fastener or a female fastener and including the above-described eyelet, is integrally molded on a tape by a method similar to that in the above U.S. patent.
In the European patent, because a specific molding method which is different from the above-described U.S Patent, is not disclosed, it is unclear how the molten resin is introduced into the cavity. However, according to FIG. 4 showing its representative embodiment, it is apparent that the molten resin is not introduced into the cavity from a inner peripheral portion of the engaging opening of a female member, because upper and lower molds for forming the engaging opening contact with each other at a parting line thereof. Therefore, the European patent is considered to be different from the U.S. patent in this point. However, if an inlet for introducing molten resin communicating with the cavity is formed at a position other than an inner peripheral engaging face of the opening, e.g., a portion adjacent to the pin member on a side for forming the opening, an resin introducing pressure is locally and directly applied to one side of the peripheral edge of the attachment hole of the tape at the beginning of introduction of the molten resin, and thus, a corrugating phenomenon is very much liable to be generated.
In order to prevent this moving phenomenon, as many pin members as possible need to be provided for clamping the tape at positions very close to the peripheral edge portion of the attachment hole. Because of this structure, the molds would be complicated. Further, it is necessary to make a setting of various and strict molding conditions for avoiding an influence of the flowing of the resin from one face of the tape to the other face.
Further, in accordance with the invention of the EP patent, as is different from the female fastener and the eyelet, the male fastener is of course a solid molded product due to the structure thereof, and further, it is necessary to mold the male fastener a column-like projection, which is an engaging portion of the male fastener, protruding from a main body of the male fastener. In order to form the male fastener having the structure mentioned above, as is different from the U.S. patent mentioned above, it is necessary to necessarily set a gate portion, which corresponds to a guide passage for introducing the molten resin into the cavity, on either one of an upper surface and a lower surface of the cavity. In the structure mentioned above, as already mentioned, in order to restrict a generation of the corrugation in the tape within the cavity, it is desired to securely nip the peripheral edge portion of the attachment hole in the tape by the pin members.
Further, in order to form the male fastener and the female fastener on the same tape, it is necessary to form cavities having different configurations in the mold. Further, in the case of changing an order of an arrangement of the male fastener and the female fastener, it is necessary to independently manufacture a mold corresponding the arrangement. This results in a complication of the mold, thus a manufacturing cost therefor is of course increased. When it is desired to avoid this, then it would be impossible to simultaneously form the male fastener and the female fastener on the same tape.
Further, as is the same as the U.S. patent mentioned above, in the fasteners with the tape mentioned above, it is unavoidable to use a single synthetic resin material for each fastener. Therefore, taking into consideration a strength of adhesion onto the tape and a strength of engagement and disengagement with respect to an opposing fastener, in order to satisfy the both, it is impossible to change a material of the adhesion portion to the tape and the fastener engaging portion. Furthermore, though it is sufficient to change a shape of the cavity in view of a shape from a viewpoint of its configuration, it is impossible to apply various colors to the same fastener.
On the contrary, as a thermoplastic resin used for this kind of snap fasteners in accordance with the conventional art, in general, a polyacetal resin is frequently used because a change of viscosity is low due to a low hygroscopic of raw material chips, a large amount of raw material chips having various colors can be stored due to little change of the material, a suitable elasticity and a suitable rigidity are provided, and it can be obtained by relatively low cost. However, since this kind of snap fasteners in accordance with the conventional art is structured such that all of the fastening members are made of a single kind of resin material as mentioned above, each of the fastening devices is unavoidably formed by a single color, so that it is too simple in color.
Further, the polyacetal resin has a relatively low melting point, each of the engaging and disengaging devices is significantly fine. For example, in the case of the male fastener, an engaging head portion which is engaged and disengaged with the female fastener protrudes outward from the surface of the fastener, the fastening device is easily melted, for example, if an iron heated to a temperature equal to or more than a melting point is accidentally brought into contact therewith when ironing, so that the engaging head portion is largely deformed or pressed and broken. Accordingly, a function as the male fastener is lost. This tends to be generated at a time of ironing at a general home where it is unavoidable to simultaneously iron various kinds of products made of various materials and it is hard to keep an ironing temperature determined in correspondence to the material.